Document cargo add's --ignore-rust-version flag

src/doc/man/cargo-add.md

@@ -123,6 +123,15 @@ crates, the features for a specific crate may be enabled with
 which enables all specified features.
 {{/option}}
 
+{{#option "`--ignore-rust-version`" }}
+Ignore `rust-version` specification in packages.
+
+This option is unstable and available only on the
+[nightly channel](https://doc.rust-lang.org/book/appendix-07-nightly-rust.html)
+and requires the `-Z unstable-options` flag to enable.
+See <https://github.com/rust-lang/cargo/issues/5579> for more information.
+{{/option}}
+
 {{/options}}
 
 

src/doc/man/generated_txt/cargo-add.txt

@@ -111,6 +111,15 @@ OPTIONS
  be enabled with package-name/feature-name syntax. This flag may be
  specified multiple times, which enables all specified features.
 
+ --ignore-rust-version
+ Ignore rust-version specification in packages.
+
+ This option is unstable and available only on the nightly channel
+ <https://doc.rust-lang.org/book/appendix-07-nightly-rust.html> and
+ requires the -Z unstable-options flag to enable. See
+ <https://github.com/rust-lang/cargo/issues/5579> for more
+ information.
+
  Display Options
  -v, --verbose
  Use verbose output. May be specified twice for “very verbose”

src/doc/src/commands/cargo-add.md

@@ -129,6 +129,14 @@ crates, the features for a specific crate may be enabled with
 which enables all specified features.</dd>
 
 
+<dt class="option-term" id="option-cargo-add---ignore-rust-version"><a class="option-anchor" href="#option-cargo-add---ignore-rust-version"></a><code>--ignore-rust-version</code></dt>
+<dd class="option-desc">Ignore <code>rust-version</code> specification in packages.</p>
+<p>This option is unstable and available only on the
+<a href="https://doc.rust-lang.org/book/appendix-07-nightly-rust.html">nightly channel</a>
+and requires the <code>-Z unstable-options</code> flag to enable.
+See <a href="https://github.com/rust-lang/cargo/issues/5579">https://github.com/rust-lang/cargo/issues/5579</a> for more information.</dd>
+
+
 </dl>
 
 

src/etc/man/cargo-add.1

@@ -140,6 +140,16 @@ crates, the features for a specific crate may be enabled with
 \fBpackage\-name/feature\-name\fR syntax. This flag may be specified multiple times,
 which enables all specified features.
 .RE
+.sp
+\fB\-\-ignore\-rust\-version\fR
+.RS 4
+Ignore \fBrust\-version\fR specification in packages.
+.sp
+This option is unstable and available only on the
+\fInightly channel\fR <https://doc.rust\-lang.org/book/appendix\-07\-nightly\-rust.html>
+and requires the \fB\-Z unstable\-options\fR flag to enable.
+See <https://github.com/rust\-lang/cargo/issues/5579> for more information.
+.RE
 .SS "Display Options"
 .sp
 \fB\-v\fR,